Grease composition for harnesses

ABSTRACT

The present invention relates to a grease composition for use in harnesses, which comprises a thickening agent, a base oil and additives, wherein the base oil comprises a polyoxyalkylene glycol ether and the additives comprise a quinoline compound and a benzotriazole compound. The grease composition is quite excellent in the corrosion resistance, the oxidation stability and the compatibility with materials such as olefinic elastomer.

BACKGROUND OF THE INVENTION

The present invention relates to a grease composition for use in a harness.

In various automotive engine accessories, in particular, harness members arranged in the proximity to an air conditioner, the condensed water originated from, for instance, the moisture present in the atmosphere may penetrate into, for instance, a connector to thus corrode metallic parts constituting the same (materials for contact parts) and therefore, these metallic parts should certainly be protected from such corrosion. In addition, a lubricant (a grease composition obtained by adding a thickening agent to a base oil and then forming the resulting blend into a semi-solid product) should satisfy, for instance, the following requirements: it should have excellent corrosion resistance and oxidation stability in order that these parts can be used over a long period of time or in order to extend the service life of the parts. Furthermore, olefinic elastomers have recently been substituted for the polyvinyl chloride as a coating material for metallic parts for the purpose of reducing the quantity of materials which may not be environment-friendly and accordingly, it has been desired to design such a grease composition while taking into consideration the compatibility thereof with the coating materials for such parts.

Conventionally, as a grease composition for filling up the distributing wire connector of a wire harness used for automobiles, there has been reported a grease composition having excellent heat resistance (Patent Document 1: JP-B-6-99702). However, this grease composition employs a purified mineral oil as a base oil and therefore, this grease composition is considered to have low compatibility with, for instance, olefinic elastomers and this composition is not designed to take into sufficient consideration the corrosion resistance and the oxidation stability.

In addition, there has also been reported a grease composition for use in a speed-reducing device (gear), which is excellent in the anticorrosive properties and which does not adversely affect materials such as rubber materials too much (Patent Document 2: JP-A-4-266995; Patent Document 3: JP-A-63-309591; and Patent Document 4: JP-A-64-29496). These grease compositions can satisfy the requirement for the compatibility with the coating materials for such parts, for instance, olefinic elastomers, but they are not always sufficient in the corrosion resistance and the oxidation stability.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide a grease composition for harnesses and more particularly to provide a grease composition for harnesses, which is excellent in the compatibility with the coating materials for parts of harnesses such as olefinic elastomers, the corrosion resistance and the resistance to oxidation.

The inventors of this invention have thus conducted various studies to eliminate the foregoing drawbacks associated with the foregoing conventional techniques concerning grease compositions for, in particular, harnesses, have found that the foregoing drawbacks can efficiently be eliminated by the use of a base oil containing a specific component and specific compounds as additives for the grease composition and have thus completed the present invention.

According to the present invention, there is thus provided a grease composition for use in harnesses, which comprises a thickening agent, a base oil and additives, wherein the base oil comprises a polyoxyalkylene glycol ether and the additives comprise a quinoline compound and a benzotriazole compound.

In a preferred embodiment of the grease composition for use in harnesses according to the present invention, the thickening agent is at least one member selected from the group consisting of lithium soaps and bentonite materials modified with organic compounds (organically modified bentonite materials).

In a further preferred embodiment of the grease composition for use in harnesses according to the present invention, the polyoxyalkylene glycol ether has a kinematic viscosity as determined at a temperature of 40° C. ranging from 30 to 400 mm²/s.

In a still further preferred embodiment of the grease composition for use in harnesses according to the present invention, the content of the quinoline compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition, and the content of the benzotriazole compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition.

The grease composition of the present invention makes use of a polyoxyalkylene glycol ether-containing base oil and comprises, as additives, a quinoline compound and a benzotriazole compound and therefore, the grease composition is excellent in the compatibility with the coating materials for parts of harnesses such as olefinic elastomers, the corrosion resistance and the resistance to oxidation.

BEST MODE FOR CARRYING OUT THE INVENTION

The grease composition of the present invention is characterized in that it uses, as a base oil, one containing a polyoxyalkylene glycol ether, which does not adversely affect the olefinic materials too much. Preferably used in the present invention are polyoxyalkylene glycol ethers represented by the following general formula I: R¹O—(CH₂CHR²O)_(n)—R³  Formula I

In Formula I, R¹ and R³ each independently represents a hydrogen atom or an alkyl group having 1 to 20, preferably 1 to 6 carbon atoms (such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group or a hexyl group); R² represents an alkyl group having 1 to 10, preferably 1 to 4 carbon atoms (such as a methyl group, an ethyl group, a propyl group or a butyl group); and n represents a numeral ranging from 5 to 30 and preferably 8 to 20, provided that R¹ and R³ do not simultaneously represent hydrogen atoms.

Specific examples of the polyoxyalkylene moieties of the polyoxyalkylene glycol ethers represented by the general formula I include polyoxyethylene, polyoxypropylene, poly(oxypropylene-oxyethylene), poly(oxybutylene-oxyethylene), poly(oxybutylene-oxypropylene), poly(oxypentylene-oxyethylene) and poly(oxypentylene-oxypropylene).

The polyoxyalkylene glycol ethers represented by the general formula I usable herein may be a mono-ether or a di-ether and specific examples thereof include polyoxypropylene monopropyl ether, polyoxypropylene monobutyl ether, polyoxybutylene monobutyl ether, polyoxyethylene oxypropylene monopropyl ether, polyoxyethylene oxypropylene monobutyl ether, polyoxyethylene oxypropylene monopentyl ether, and polyoxypropylene dimethyl ether. Preferred are polyoxypropylene monobutyl ether, and polyoxypropylene dimethyl ether, most preferred is polyoxypropylene dimethyl ether.

Preferably, the base oil used in the present invention comprises a polyoxyalkylene glycol ether in an amount of preferably not less than 50% by mass, more preferably not less than 80% by mass and most preferably 100% by mass on the basis of the total mass of the base oil. The base oil used in the present invention may further comprise other base oil materials currently used in the grease composition such as mineral oils, synthetic hydrocarbon oils, and alkyl diphenyl ether oils in addition to the polyoxyalkylene glycol ether, but the amount thereof is preferably less than 10% by mass on the basis of the total mass of the base oil.

The kinematic viscosity of the polyoxyalkylene glycol ether as determined at 40° C. preferably ranges from 30 to 400 mm²/s and more preferably 80 to 120 mm²/s.

As the thickening agent used in the grease composition for harnesses according to the present invention, there may be listed, for instance, those conventionally known in this art such as metal salts of fatty acids, bentonite modified with organic compounds and PTFE, with metal salts of fatty acids and bentonite modified with organic compounds being particularly preferably used herein.

As the constituent fatty acids of the foregoing metal salts of fatty acids, preferably used herein are those having 10 to 30 and more preferably 16 to 20 carbon atoms and examples thereof preferably used herein are lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxy stearic acid and oleic acid. Moreover, as the metal salts of these fatty acids, there may be mentioned, for instance, alkali metal salts such as sodium and lithium salts, alkaline earth metal salts such as barium and calcium salts and trivalent metal salts such as aluminum salts. Usable herein further include, for instance, salts of mixtures each comprising at least two fatty acids including dibasic acids with metals such as aluminum, calcium and lithium, or complex metallic soaps. Among these metal salts of fatty acids, most preferably used herein is lithium 12-hydroxy stearate because of its excellent water resistance, heat resistance and mechanical stability.

The amount of the thickening agent to be incorporated into the grease composition of the present invention preferably ranges from 2 to 35 parts by mass and more preferably 5 to 15 parts by mass per 100 parts by mass of the base oil. This is because, if the amount thereof is less than 2 parts by mass, there would be observed such a tendency that the resulting grease composition is in a highly fluidized state and it is thus too soft, while if the amount thereof exceeds 35 parts by mass, the resulting composition is liable to be too hard to use as a grease composition for harnesses.

Examples of quinoline compounds used in the grease composition for harnesses according to the present invention are compounds represented by the following general formula II, such as trimethyl dihydro-quinoline oligomer.

In Formula II, R⁴, R⁵ and R⁶ may be the same or different and each preferably represents an alkyl group preferably having 1 to 10 and more preferably 1 to 3 carbon atoms and n is a numeral preferably ranging from 1 to 10 and more preferably 1 to 5.

Particularly preferred such quinoline compounds are, for instance, trimethyl dihydro-quinoline oligomers (n=2 to 3).

The amount of these quinoline compounds to be incorporated into the grease composition of the present invention preferably ranges from 0.1 to 10% by mass, more preferably 0.5 to 5% by mass and most preferably 1.0 to 3% by mass on the basis of the total mass of the grease composition.

The grease composition of the present invention may further comprise other anti-oxidants, for instance, a phenolic compound such as 2,6-di-t-butyl cresol and/or an amine compound such as phenyl-α-naphthyl-amine, in combination with the foregoing components. In this respect, the content thereof used herein is desirably not more than 5.0% by mass on the basis of the total mass of the grease composition.

The grease composition for harnesses according to the present invention may comprise a benzotriazole compound as the corrosion inhibitor. Examples of such benzotriazole compounds preferably used herein are those represented by the following general formula III:

In Formula III, R⁷ represents a hydrogen atom or an alkyl group having 1 to 10 and preferably 1 to 3 carbon atoms such as a methyl, ethyl or propyl group, R⁸ and R⁹ each independently represents a hydrogen atom or an alkyl group having 1 to 20 and preferably 1 to 10 carbon atoms such as a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, heptyl or octyl group. Particularly preferably used herein are, for instance, benzotriazole compounds represented by the general formula III in which R⁷ represents a methyl group and R⁸ and R⁹ each represents a 2-ethylhexyl group.

The content of the benzotriazole compound present in the grease composition of the present invention preferably ranges from 0.1 to 10% by mass, more preferably 0.3 to 5% by mass and most preferably 0.5 to 3% by mass on the basis of the total mass of the grease composition.

The grease composition of the present invention may comprise a corrosion inhibitor other than the foregoing benzotriazole compound, such as succinic acid compound, typical of an alkenyl succinic acid anhydride, and/or sulfonic acid compound represented by an alkyl naphthalene-sulfonic acid in combination with the triazole type one and the amount thereof to be used is desirably not more than 5.0% by mass on the basis of the total mass of the grease composition.

The present invention will hereunder be described in more detail with reference to the following non-limitative Examples and Comparative Examples, but the present invention is not restricted to these specific Examples at all.

EXAMPLES 1 TO 6 AND COMPARATIVE EXAMPLES 1 TO 6

In these Examples, there were prepared a variety of grease compositions each comprising a thickening agent, a base oil and additives specifically listed below and then characteristic properties thereof were evaluated according to the methods detailed below:

(Sample Grease Compositions)

Thickening Agent:

Lithium soap (lithium 12-hydroxy-stearate)

Bentonite modified with an organic compound (organically modified bentonite)

Base Oil:

Polyoxypropylene dimethyl ether (n=20): Kinematic viscosity (at 40° C.): 95 mm²/s;

Polyoxypropylene monobutyl ether (n=10): Kinematic viscosity (at 40° C.): 105 mm²/s;

Dioctyl sebacate: Kinematic viscosity (at 40° C.): 12 mm²/s.

Additives:

Quinoline compound (trimethyl dihydro-quinoline oligomer);

Benzotriazole compound (a mixture comprising 1-[N,N-bis(2-ethylhexyl)-aminomethyl]-4-methyl benzotriazole and 1-[N,N-bis(2-ethylhexyl)-aminomethyl]-5-methyl benzotriazole);

Phenolic compound (octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate);

Succinic acid compound (alkenyl succinic acid anhydride).

1. Test of Thin Film Under High Temperature and High Humidity Conditions (Test for Corrosion Resistance)

A candidate grease composition was applied onto the lower half of the surface of a copper sheet, a brass sheet or tin-plated sheet, in a thickness of 2 mm, followed by allowing each sheet to stand at 60° C., 80% RH for 168 hours and the subsequent confirmation of whether each test material underwent any external color change or not. The corrosion resistance of each test material was evaluated according to the following evaluation criteria:

◯: The test material is not subjected to any corrosion;

-   x: The test material is in fact subjected to corrosion.     2. Test for Oxidation Stability

Method for Determination: This was determined according to JIS K 2220. 12. (99° C., 100 hours) and was evaluated on the basis of the following evaluation criteria:

◯: Less than 50 kPa;

x: Not less than 50 kPa.

3. Olefin-Immersion Test (Compatibility with Material)

Polypropylene elastomer (having a size of 50 mm×5 mm×1 mm) was immersed in each sample grease composition (100 g) maintained at 80° C. for 96 hours and then each olefinic material was inspected for the volume change according to the following equation: Volume Change(%)=100×(A−B)/A

In the equation, A represents the volume of each elastomer observed prior to the immersion test and B the volume thereof observed after the immersion test. Each sample was evaluated on the basis of the following criteria:

◯: The sample elastomer has a volume change of less than ±10%;

x: The sample elastomer has a volume change of not less than ±10%.

The results thus obtained are summarized in the following Tables 1 and 2: TABLE 1 Ex. No. 1 2 3 4 5 6 Thickening Agent Lithium hydroxy-stearate 10.0 10.0 10.0 10.0 10.0 Organically modified 10.0 bentonite Base Oil Polyoxypropylene 89.0 86.0 86.0 80.0 86.0 dimethyl ether Polyoxypropylene 86.0 monobutyl ether Dioctyl sebacate Additives Quinoline compound 0.5 1.0 3.0 5.0 3.0 3.0 Phenolic compound Benzotriazole compound 0.5 3.0 1.0 5.0 1.0 1.0 Succinic acid compound Worked Penetration 280 280 280 280 280 280 Corrosion Resistance ◯ ◯ ◯ ◯ ◯ ◯ (60° C., 80% RH × 168 hr) Oxidation Stability ◯ ◯ ◯ ◯ ◯ ◯ (99° C. × 100 hr) Olefin-Immersion Test ◯ ◯ ◯ ◯ ◯ ◯ (80° C. × 96 hr)

TABLE 2 Comp. Ex. No. 1 2 3 4 5 6 Thickening Agent Lithium hydroxy-stearate 10.0 10.0 10.0 10.0 10.0 Organically modified 10.0 bentonite Base Oil Polyoxypropylene 87.0 89.0 86.0 86.0 dimethyl ether Polyoxypropylene 86.0 monobutyl ether Dioctyl sebacate 86.0 Additives Quinoline compound 3.0 3.0 3.0 Phenolic compound 3.0 3.0 Benzotriazole compound 1.0 1.0 Succinic acid compound 1.0 1.0 1.0 Worked Penetration 280 280 280 280 280 280 Corrosion Resistance X X X X X X (60° C., 80% RH × 168 hr) Oxidation Stability ◯ X X ◯ ◯ X (99° C. × 100 hr) Olefin-Immersion Test ◯ ◯ ◯ ◯ X ◯ (80° C. × 96 hr)

The data listed in the foregoing Tables 1 and 2 clearly indicate that the grease compositions prepared in Examples 1 to 6 according to the present invention can provide excellent results in the test of thin film under high temperature and high humidity conditions, the test for oxidation stability and the olefin-immersion test, or that these grease compositions are quite excellent in the corrosion resistance, the oxidation stability and the compatibility with olefinic material, since the grease composition of the present invention comprises a polyoxyalkylene glycol ether as the base oil and a quinoline compound and a benzotriazole compound as the additives.

On the contrary, the data listed in the foregoing Tables 1 and 2 likewise clearly indicate that the grease compositions prepared in Comparative Examples 1 and 4, which are free of any benzotriazole compound, are inferior in the corrosion resistance, that the grease compositions prepared in Comparative Examples 2 and 3, which are free of any quinoline compound, are insufficient in the corrosion resistance and the oxidation stability and that the grease composition prepared in Comparative Example 5, which makes use of dioctyl sebacate as the base oil and a succinic acid compound in place of the benzotriazole compound, are inferior in the corrosion resistance and the compatibility with olefinic material. Moreover, it is clear from the foregoing data that the grease composition prepared in Comparative Example 6 (a commercially available grease composition), which is free of the both quinoline type and benzotriazole compounds, is inferior in the both corrosion resistance and oxidation stability. 

1. A grease composition for use in harnesses, which comprises a thickening agent, a base oil and additives, wherein the base oil comprises a polyoxyalkylene glycol ether and the additives comprise a quinoline compound and a benzotriazole compound.
 2. The grease composition for use in harnesses as set forth in claim 1, wherein the thickening agent is at least one member selected from the group consisting of lithium soaps and bentonite modified with organic compounds.
 3. The grease composition for use in harnesses as set forth in claim 1, wherein the polyoxyalkylene glycol ether has a kinematic viscosity as determined at a temperature of 40° C. ranging from 30 to 400 mm²/s.
 4. The grease composition for use in harnesses as set forth in claim 1, wherein the content of the quinoline compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition and the content of the benzotriazole compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition.
 5. The grease composition for use in harnesses as set forth in claim 2, wherein the polyoxyalkylene glycol ether has a kinematic viscosity as determined at a temperature of 40° C. ranging from 30 to 400 mm²/s.
 6. The grease composition for use in harnesses as set forth in claim 2, wherein the content of the quinoline compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition and the content of the benzotriazole compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition.
 7. The grease composition for use in harnesses as set forth in claim 3, wherein the polyoxyalkylene glycol ether has a kinematic viscosity as determined at a temperature of 40° C. ranging from 30 to 400 mm²/s.
 8. The grease composition for use in harnesses as set forth in claim 3, wherein the content of the quinoline compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition and the content of the benzotriazole compound ranges from 0.1 to 10% by mass on the basis of the total mass of the grease composition. 